1. Technical Field
The invention relates to a zoom lens device for moving plural lens holding frames simultaneously in an optical axis direction by rotating a cam barrel with respect to a fixed barrel.
2. Description of the Related Art
For example, JP Hei. 4-57007 A discloses a zoom lens device including a cam mechanism, which causes a lens group held by the lens holding frame to move in an optical axis direction by rotating a cum barrel with respect to a fixed barrel during varying of power and guiding a cam follower provided on the lens holding frame to an intersection point between a cam face provided spirally on the cam barrel and a straight moving guiding face provided in the fixed barrel.
A higher power of the zooming power and a reduction in size are required of zoom lens devices. In order to attain a higher power, it is necessary to set a displace amount of the cam face in the optical axis direction to be long to extend a movement amount of lens groups constituting the zoom lens. Also, in order to move simultaneously plural lens groups each having a different movement amount during varying of a power by using one cam barrel, it is necessary to form plural cam faces, whose displace amount in the optical axis direction are long, in on the cam barrel. In this case, if a diameter of the cam barrel is small, an angle between the cam faces and the rotation direction become sharp. A large torque is required to rotate the cam face, and also it is difficult to move the cam follower smoothly. As a result, it is the present situation that it is necessary to increase a diameter of the can barrel contrary to a demand for compactification.